This invention relates to a speech recognition system with an accurate recognition function, and in particular, to a system as one kind of data input device with an accurate recognition function which can eliminate any recognition error.
A conventional speech recognition system of this type comprises a microphone for inputting speech, a speech recognition circuit for registering and recognizing the speech input signal from the microphone, a central processing unit (CPU) for reading a recognition output from the speech recognition circuit and allowing data corresponding to the recognition data to be transmitted to a speech synthesizer via a data bus, a speech synthesizer for receiving data from the CPU and synthesizing the speech from the data, and a speaker for outputting the speech which is synthesized by the speech synthesizer.
According to this system, the user can input data and give an instruction without using his hands, and in fact, it proves very useful when applied to an input device. In this system, however, whether or not the recognition output from the speech recognition circuit is wrong is ascertained by the output of the speech synthesizer. Only predetermined speech patterns are written with respect to the speech synthesizer, placing some restriction upon the speech inputs through the speaker Since the input speech does not always coincide with the registered speech patterns, it is difficult for the user to ascertain their coincidence. This causes uneasiness in the user. During the speech registration process, it is necessary to register the speech input at a predetermined address position in a memory of the speech recognition circuit, thus involving a cumbersome operation.
Furthermore, since with respect to a respective word or clause one kind of speech pattern is registered for comparison with the speech input, even if the same user inputs his own speech, it is not often successfully recognized due to ambient noise and the delicately varying speech input characteristic. Where, in particular, the speech recognition system is employed as an input device for a mobile station such as in a moving vehicle, the speech is liable to be varied due to the acoustic circumstances within the narrow confines of the vehicle compartment and the traffic noise on the road, resulting in a poor recognition percentage.
Where the speech recognition system is used as the input device for automobile telephones, the telephone set per se never has a speech recognition ascertaining function and, therefore, it is not possible for the user to ascertain that the speech input has been correctly recognized, unless it is sent back from a central station.